//
// interpreter.hpp
// curly
//
// Created by Bob Polis at 2020-09-05
// Copyright (c) 2020 SwiftCoder. All rights reserved.
//

#ifndef _interpreter_H_
#define _interpreter_H_

#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <stdexcept>

class syntax_error : public std::runtime_error {
    public:
        syntax_error(const std::string& what_arg, size_t lineno)
            : std::runtime_error {what_arg}, _lineno {lineno} {}
        size_t lineno() const { return _lineno; }
    private:
        size_t _lineno {0};
};

class interpreter {
    public:
        interpreter() = default;

        std::string eval(std::istream& in, bool& done);

    private:
        std::vector<std::string> _prog; // program lines without label defs or comments
        std::vector<std::string> _values; // value stack
        std::vector<size_t> _calls; // call stack
        std::map<std::string, size_t> _labels; // label name => prog line index
        std::map<std::string, std::string> _vars; // variable name => string value
        size_t _pc {0}; // current program counter (index into _prog)
        std::vector<size_t> _pc_offsets; // removed line indices for: prog index => source line

        void reset();
        void exec_instruction(const std::string& code, bool& done);
        
        // integer operations
        void add();
        void sub();
        void mul();
        void div();
        void mod();
        void abs();
        void neg();
        void inc();
        void dec();

        // string operations
        void dup();
        void rev();
        void slc();
        void idx();
        void cat();
        void len();
        void rot();
        void enl();

        // tests & jumps
        void gto();
        void geq();
        void gne();
        void glt();
        void gle();
        void ggt();
        void gge();

        // subroutines
        void fun();
        void ret();

        // I/O
        void inp();
        void out();
        void err();
};

#endif // _interpreter_H_